Effects of Swirl Number and Central Rod on Flow in a Lean Premixed Swirl Combustor

ABSTRACT

In most modern-day lean gas turbine combustors, flame is stabilized by swirl flows. A central toroidal recirculation zone (CTRZ), developed by these swirl flows, helps to stabilize the flame. The current study is focused on the effects of swirl number and a central rod on the flow behavior in a lean premixed swirl-stabilized combustor. Turbulence is modeled using the two-equation, realizable k-ϵ model of Reynolds-Averaged Navier–Stokes (RANS), and flamelet generated manifold (FGM) technique is used to model combustion. Both swirl number and central rod have a very significant effect on the flow and the flame in the combustor. The CTRZ moves upstream along with the flame, creating a flashback, with an increase in the swirl number. Also, the presence of a central rod accelerates the flame flashback at high swirl numbers. Higher turbulence is observed in inner shear layers, especially at high swirl numbers. $\mathrm{N}{\mathrm{O}}_{\mathrm{x}}$ emissions are higher in the regions of high temperature, especially in the CTRZ. These emissions decrease with the increase in the swirl intensities. At low swirl numbers, the case with the central rod exhibits lower $\mathrm{N}{\mathrm{O}}_{\mathrm{x}}$ production, and at high swirl numbers, the case without the central rod yields better results in the $\mathrm{N}{\mathrm{O}}_{\mathrm{x}}$ mitigation.

KEYWORDS:

• Swirl number
• lean premixed combustion
• swirl-stabilized combustion
• flamelet generated manifold
• computational fluid dynamics

Acknowledgements

The authors would like to thank Ohio Supercomputer Center (Center 1987) for their continuous support and allocation of computing time

Disclosure statement

No potential conflict of interest was reported by the author(s).